1. Field of the Invention
The present invention relates to a toner cartridge for supplying toner for a developing unit in image forming apparatuses such as a laser printer, a copier and the like.
2. Description of the Related Art
A conventional toner cartridge will be explained with reference to FIGS. 4 to 7. In FIG. 5, toner 2 is stored in a container 1, and a cap 3 is disposed on an opening portion of the container 1, which has an opening portion 3a in the shape of a semicircle. A shutter 6 is rotatably attached to an edge of the semicircle opening portion 3a of the cap 3, and has an opening portion 6a that is substantially the same shape as the opening portion 3a. A sponge 5 has substantially the same shape as a face of the shutter 6 facing the cap 3, and defines an opening portion 5a having substantially the same shape as the opening portions 3a and 6a. The sponge 5 is attached to the shutter 6 so that the opening portions 5a and 6a correspond to each other. The sponge 5 is pressed by the shutter 6 when the shutter 6 is attached to the cap.
When the shutter 6 is closed, the semicircle opening portion 6a of the shutter 6 has a reverse phase relation of 180xc2x0 with respect to the semicircle opening portion 3a of the cap. The semicircle opening portion 3a of the cap is covered with the sponge 5 and sealed, thereby preventing the toner 2 from leaking. When the toner cartridge is used, the shutter 6 is rotated by 180xc2x0. Therefore, as shown in FIGS. 8 and 9, the opening portions 3a, 5a and 6a correspond to each other, thereby supplying the toner 2 from the toner cartridge.
However, in the case of the aforementioned structure, the sponge 5 is merely pressed to seal the opening portion. Therefore, if a volume of the container portion 1 increases, and a diameter of the semicircle opening portion 6a is enlarged while a thickness of the shutter 6 is not changed to prevent the toner supply from leaking from the toner cartridge, there arise problems that stiffness of the center seal portion 6b of the shutter 6 weakens, and a portion in the vicinity of the center of the shutter 6 is deformed to project upward by reaction of the pressed sponge so that the volume amount of the pressed sponge 5 is reduced from the predetermined amount. Therefore, the seal efficiency is deteriorated, and the toner is leaked from the toner cartridge due to vibrations, temperature changes, atmosphere changes, and the like, when the toner cartridge is transported.
On the other hand, if the volume amount of the pressed sponge is increased on order to securely seal the opening portion, friction resistance of the sponge 5 increases. Therefore, a torque for rotating the shutter 6 also increases, which results in that the shutter 6 is difficult to operate. Moreover, if the toner cartridge has a structure with a high stiffness not to deform the shutter 6, the thickness of the shutter increases, thereby enlarging the cartridge itself.
An object of the present invention is to provide a toner cartridge in which toner is not leaked even if the volume of the toner cartridge increases without the thickness of a shutter being increased.
According to the present invention, there is provided a toner cartridge comprising:
a container for containing toner of a volume of 2500 cm3 or more, the container defining an opening portion;
a cap fixed to the opening portion of the container, the cap defining a first semicircle opening portion;
a film covering and sealing the first semicircle opening portion of the cap; and
a shutter rotatably disposed on the cap; the shutter defining a second semicircle opening portion capable of corresponding to the first semicircle opening portion of the cap, the shutter having a diameter of 70 mm or above.
The toner cartridge may be made, wherein the film is allowed to be peeled off the cap with the shutter closed.